The present invention relates to an apparatus for defining a position of a lens, more specifically, to an improvement of an apparatus for defining a position of a lens along the direction of an optical axis and a rotation thereof in order to control a position of a lens relative to a camera body in the direction of the optical axis.
A camera having an auto-focusing device is known in which a lens actuating member to which a lens is attached is rotatably supported on a cylindrical member for movement about an optical axis thereof, and the lens actuating member and cylindrical member are interconnected through a cam mechanism. The cam mechanism is provided with a cam which is formed on the cylindrical member and a protrusion which is provided on the lens actuating member and engaging with the cam. When the lens actuating member rotates about the optical axis of the lens in accordance with the result of measuring the distance between the camera and the object to be photographed, the position thereof in the direction of the optical axis is changed in accordance with a profile of the cam, thereby adjusting the focal length of the lens. In order to cause the protrusion of the lens actuating member to always contact the profile surface of the cam, a first spring for urging the lens actuating member in the direction of the optical axis and a second spring for urging it in the rotating direction are provided between the lens actuating member and camera body.
The first spring, however, is provided in front of the lens actuating member to urge it toward the cam which is provided behind thereof. Accordingly, the total length of a lens part incorporated with the cylindrical member and lens actuating member in the direction of the optical axis is enlarged. Furthermore, it should be necessary to employ the first and second springs to accomplish the auto-focusing operation. It should noted that the camera includes a camera body which has a main body in which film is loaded and a lens cover which is integrally attached to the front surface of the main body and in which the lens enclosed in the cylindrical member is contained.
As a result, in the conventional camera with the first and second springs, a protruding amount of the lens cover from the front surface of the main body is relatively large, so that it is difficult to make the conventional camera compact.